ACOUSTIC SCATTERING BY TWO SPHERES: MULTIPLE SCATTERING AND SYMMETRY CONSIDERATIONS

Acoustic scattering by two identical spheres is theoretically, numerically and experimentally studied by highlighting the role of the symmetries of the scatterer. Incident and scattered fields are expanded over the different irreducible representations of D∞h, the continuous symmetry group of the scatterer. Then, from the boundary conditions, one obtains for each irreducible representation an infinite system of linear complex algebraic equations where the unknown scattering coefficients are uncoupled. This feature greatly simplifies the treatment of the problem and speeds up calculations. Farfield form functions are computed in the cases of Neumann boundary conditions (rigid spheres) and elastic boundary conditions (elastic spheres immersed in water). A series of experiments based on ultrasonic spectroscopy is performed in the case of two stainless-steel spheres immersed in water. The comparison between the theoretical and the experimental results provides quite a good agreement.